Health officials have been warning us about antibiotic overuse and drug-resistant "superbugs" for a long time. But today the Centers for Disease Control and Prevention is sounding the alarm in a new way.

For the first time, the CDC is categorizing drug-resistant superbugs by threat level. That's because, in their conservative estimates, more than 2 million people get antibiotic-resistant infections each year, and at least 23,000 die because current drugs no longer stop their infections.

Antibiotics are designed to kill bacteria that cause infection. However, in the process they can also kill so-called good bacteria (the human body hosts about 100 trillion).

The Missouri Department of Health explains it this way: "Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply. Repeated and improper uses of antibiotics are primary causes of the increase in drug-resistant bacteria."